Roche said the study in the first of three trial stages required for regulatory approval showed the compound known as CT-388 yielded weight loss of 18.8%, when adjusted for a placebo effect, after 24 weeks in otherwise healthy adults with obesity.
The shares were up 4% at 0847 GMT, on track for their best one-day performance since September 2022.
Once-a-week injection CT-388 is Carmot's most promising drug candidate, mimicking the effect of two gut hormones - GLP-1 and GIP - like Lilly's (LLY.N) Mounjaro, also known as Zepbound.
With a new generation of obesity drugs expected to vie for a market seen as large as $100 billion, even early-stage trial read-outs have been boosting share prices.
“The results are highly encouraging for further development of CT-388 for both obesity and type 2 diabetes and underscore its potential to become a best-in-class therapy with durable weight loss and glucose control.” said Roche’s Chief Medical Officer Levi Garraway.
One trader said the gain in Roche's stock was also supported by some investors seeking to cover previous short positions, or bets on a falling share price.
Roche also said all of CT-388 treated participants achieved a weight loss of more than 5%, while 70% achieved more than 15% weight loss and 45% achieved more than 20%.
Analysts at Citi cautioned that incumbent Lilly with Zepbound was well entrenched and that Novo's CagriSema, an experimental drug that is further advanced in development than CT-388, would likely have comparable results.
"While certainly impressive, this data (by Roche) does not raise the bar," the analysts wrote in a note.
Still, shares in rival Zealand Pharma (ZELA.CO), which is working on a new weight-loss drug with Boehringer Ingelheim, dropped 5%. Novo stock was little changed.
A Roche spokesperson said the placebo-adjusted read-out was a result of 18.9 % weight loss in patients on CT-388 and of just 0.1% weight loss in a comparative group on placebo, with 31 trial participants considered overall.
She added further data from a wider CT-388 Phase 1 trial on obese patients with diabetes was expected towards the end of the year.
More Phase 1 trial data on another Carmot drug candidate, CT-996, was expected in June or July, the company said.
